đấy có phải lớp 4 ko đấy

Lớp 4 đó nếu ai ko làm được thì ko phải học sinh giỏi đó nha

Gọi A = 1/1.6 + 1/6.11 +...+ 1/(5n+1)(5n+6) 

5A = 5/1.6 + 5/6.11 + ... + 5/(5n+1)(5n+6)

     =1 - 1/6 + 1/6 - 1/11 + ... + 1/5n+1 - 1/5n+6 

    =1 - 1/5n+6 =5n+6/5n+6 - 1/5n+6=5n+5 /5n+6

tôi không hiểu???

Mình có 1 bài cho bạn tham khảo ( mình tự viết đó )

         Riêng mặt trời chỉ có một mà thôi

         Và mẹ em chỉ có một trên đời.

Mỗi khi ngân nga câu hát này ,tôi lại nghĩ về mẹ. Mẹ là người đã dùi dắt em khôn lớn từng ngày. Đối với em , nếu bố là chỗ dựa thì mẹ là người quan trọng nhất.

Em cần phần nào nhỉ .

A = \(\dfrac{5}{1.6}\)+\(\dfrac{5}{6.11}\)+\(\dfrac{5}{11.16}\)+\(\dfrac{5}{16.21}\)+...+\(\dfrac{5}{101.106}\)

A = \(\dfrac{1}{1}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{11}+...+\dfrac{1}{101}-\dfrac{1}{106}\)

A = \(\dfrac{1}{1}\) - \(\dfrac{1}{106}\)

A = \(\dfrac{105}{106}\)

B = \(\dfrac{3}{1.4}\) +\(\dfrac{3}{4.7}\)+\(\dfrac{3}{7.10}\)+...+\(\dfrac{3}{97.100}\)

B = \(\dfrac{1}{1}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{97}-\dfrac{1}{100}\)

B = \(\dfrac{1}{1}\) - \(\dfrac{1}{100}\)

B = \(\dfrac{99}{100}\)

C = \(\dfrac{1}{2.7}+\dfrac{1}{7.12}\) + \(\dfrac{1}{12.17}\)+...+ \(\dfrac{1}{97.102}\)

C= \(\dfrac{1}{5}\) \(\times\)( \(\dfrac{5}{2.7}+\dfrac{5}{7.12}+\dfrac{5}{12.17}+...+\dfrac{5}{97.102}\))

C = \(\dfrac{1}{5}\)\(\times\)(\(\dfrac{1}{2}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\) - \(\dfrac{1}{12}\) + \(\dfrac{1}{12}\) - \(\dfrac{1}{17}\)+...+ \(\dfrac{1}{97}\) - \(\dfrac{1}{102}\))

C = \(\dfrac{1}{5}\) \(\times\)( \(\dfrac{1}{2}\) - \(\dfrac{1}{102}\))

C = \(\dfrac{1}{5}\) \(\times\) \(\dfrac{25}{51}\)

C = \(\dfrac{5}{51}\) 

D = \(\dfrac{1}{2}\) +   \(\dfrac{1}{6}\) + \(\dfrac{1}{12}\) + \(\dfrac{1}{20}\) + \(\dfrac{1}{30}\) + \(\dfrac{1}{42}\) + \(\dfrac{1}{56}\) + \(\dfrac{1}{72}\)

D = \(\dfrac{1}{1.2}\) + \(\dfrac{1}{2.3}\) + \(\dfrac{1}{3.4}\) + \(\dfrac{1}{4.5}\) + \(\dfrac{1}{5.6}\) + \(\dfrac{1}{6.7}\)+\(\dfrac{1}{7.8}\)+ \(\dfrac{1}{8.9}\)

D = \(\dfrac{1}{1}\) - \(\dfrac{1}{2}\)+\(\dfrac{1}{2}\)-\(\dfrac{1}{3}\)+\(\dfrac{1}{3}\)-\(\dfrac{1}{4}\)+\(\dfrac{1}{4}\)-\(\dfrac{1}{5}\)+\(\dfrac{1}{5}\)-\(\dfrac{1}{6}\)+\(\dfrac{1}{6}\) - \(\dfrac{1}{7}\)+\(\dfrac{1}{7}\)-\(\dfrac{1}{8}\)+\(\dfrac{1}{8}\)-\(\dfrac{1}{9}\)

D = \(\dfrac{1}{1}\) - \(\dfrac{1}{9}\)

D = \(\dfrac{8}{9}\)

E = \(\dfrac{3}{2.4}\)+\(\dfrac{3}{4.6}\)+\(\dfrac{3}{6.8}\)+...+\(\dfrac{3}{98.100}\)

E = \(\dfrac{3}{2}\) \(\times\) ( \(\dfrac{2}{2.4}\) + \(\dfrac{2}{4.6}\)+ \(\dfrac{2}{6.8}\)+...+\(\dfrac{2}{98.100}\))

E = \(\dfrac{3}{2}\)\(\times\)( \(\dfrac{1}{2}\) - \(\dfrac{1}{4}\)+ \(\dfrac{1}{4}\) - \(\dfrac{1}{6}\)+\(\dfrac{1}{6}\)-\(\dfrac{1}{8}\)+...+\(\dfrac{1}{98}\) - \(\dfrac{1}{100}\))

E = \(\dfrac{3}{2}\) \(\times\) ( \(\dfrac{1}{2}\) - \(\dfrac{1}{100}\))

E = \(\dfrac{3}{2}\) \(\times\) \(\dfrac{49}{100}\)

E = \(\dfrac{147}{200}\)

Tiếng trống giờ ra chơi đã vang lên bên tai mỗi học sinh. Từ các lớp, học sinh ùa ra như những chú chim non, tò mò muốn bước ra ngoài không gian.

Nắng đuổi bắt chùm lộc non xanh mơn mởn, rồi đứng lại bên những cành phượng vĩ đỏ rực đang khoe sắc. Dưới gốc cây đa già sừng sững, các bạn gái rủ nhau chơi nhảy dây. Những đôi chân xinh xắn ấy, cùng bạn nhảy dây từng bước uyển chuyển. Bạn nào bạn nấy cũng cố gắng nhảy thật nhịp nhàng, để đáp lại sự cổ vũ nhiệt tình của các bạn xung quanh. Ngỡ rằng, đây chính là những thiên thần bé nhỏ, đang chơi đùa trong khung cảnh ngây thơ, trong sáng của tuổi học trò. Gần đó là trò chơi đá cầu cũng lí thú không kém.

Quả cầu nhiều màu sắc như bảy màu tinh tú của cầu vồng. Nó được đôi chân khoẻ khoắn, nhanh nhẹn của các bạn nam làm cho có sức sống. Chẳng có thể nhìn thấy quả cầu xinh xinh đâu nữa, mà chỉ thấy đôi chân nhanh nhẹn thoắt lên, thoắt xuống của các bạn. mấy bạn đứng xem, người thì chăm chú nhìn quả cầu tung lên hạ xuống, người thì trổ tài dự đoán xem bàn chân nào khéo nhất. Cuối cùng, bạn nam lớp tôi cũng giành chiến thắng bởi những cú đá hiểm hóc.

Thật sung sướng! Khi nhận được danh hiệu mà các bạn yêu thích tăng cho đó là: “quả cầu thần”. Có bạn muốn tìm cho mình một sự thư giãn nhẹ nhàng, lại đến bên gốc bàng xanh mướt kia ngồi đọc những cuốn sách lí thú. Vẻ chăm chú ấy làm cho ai cũng tin rằng đó là những cô gái, chàng trai sẽ là những tinh hoa cho xã hội, làm nên một cuộc sống tươi đẹp cho chính mình và cả đất nước. Với những “nhà thơ nhí” luôn thả mình vào trong bầu không khí sôi động, hồn nhiên, để có thể nảy ra những vần thơ chứa chan thi vị. Ngược lại, các bạn trai hiếu động lại tìm thấy niềm vui riêng trong trò chơi đuổi bắt. Mồ hôi nhễ nhại toát ra như tắm, nhưng dường như nó chẳng là gì đối với các bạn, bởi lẽ ai cũng thấy lòng rộn lên niềm vui của trẻ thơ. Vì là một vận động viên điền kinh, nên bảo luôn là một “đối thủ” đáng gờm.

Chẳng vậy, mà bạn nào bạn nấy cũng cố gắng thoát khỏi vòng vây của Bảo “vận động viên điền kinh tương lai”. Chị gió tốt bụng dùng chiếc quạt của mình xua tan cái nắng nóng cho cả sân trường. Những bạn gái nhút nhát, dịu dàng lại luôn quây quần lại luôn quây quần bên gốc cây phượng vĩ tâm sự về mọi việc mà các bạn cho là lí thú nhất. Sân trường vui thật đấy! Làm cho các chú chim sâu cũng phải ngó xuống nhìn. Những chùm hoa sữa nở rộ toả hương thơm quyến rũ, dù chỉ với bông hoa li ti, trắng muốt. Trên không trung, ông mặt trời cháy bỏng, ngó xuống nhìn nở nụ cười với đàn em thơ đang nô đùa.

Bỗng ba hồi trống vang lên, các bạn học sinh lần lượt vào lớp, ai cũng tươi tắn như những đoá hoa ban mai. Bởi các bạn sắp bước vào những tiết học sôi nổi hào hứng. Giờ ra chơi ở trường em là vậy đó, nó mang lại cho chúng em biết bao kỉ niệm thân thương, dưới mái trường mến yêu.

bài nào

dạ chào oog cháu xin trả lời 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1 + 1 = 2

Nội qui tham gia "Giúp tôi giải toán"

1. Không đưa câu hỏi linh tinh lên diễn đàn, chỉ đưa các bài mà mình không giải được hoặc các câu hỏi hay lên diễn đàn;

2. Không trả lời linh tinh, không phù hợp với nội dung câu hỏi trên diễn đàn.

3. Không "Đúng" vào các câu trả lời linh tinh nhằm gian lận điểm hỏi đáp.

Các bạn vi phạm 3 điều trên sẽ bị giáo viên của Online Math trừ hết điểm hỏi đáp, có thể bị khóa tài khoản hoặc bị cấm vĩnh viễn không đăng nhập vào trang web.

\(\frac{2}{1x6}+\frac{2}{6x11}+\frac{2}{11x16}+\frac{2}{16x21}+\frac{2}{21x26}\)

= \(\frac{2}{6}+\frac{2}{66}+\frac{2}{176}+\frac{2}{336}+\frac{2}{546}\)

= \(\frac{1}{3}+\frac{1}{33}+\frac{1}{88}+\frac{1}{168}+\frac{1}{273}\)

=\(\frac{5}{13}\)

Mình tự nghĩ đấy .

Chúc bạn học tốt!

Em rút ra được là:

Thà mình hỏi mình ngu trong 1 chút nhưng sau đó mình hiểu, còn hơn là mình giấu ngu thì mình sẽ không biết và sẽ dốt cả đời

Cảm ơn bạn